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If "warm" amplifier makes difference ..

sngreen

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What exactly is happening that makes warm amplifier sound better than the cold one (when it first started)? This in fact applies to the other components as well; phono-stage, pre, ..etc. but is it equally the same?

Can this change be measured?

thanks
 

xaviescacs

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By "warm" you mean a flat frequency response and by "cold" a one with boosted upper highs (roughly, from 12 to 20 kHz)?
 
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sngreen

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By "warm" you mean a flat frequency response and by "cold" a one with boosted upper highs (roughly, from 12 to 20 kHz)?

I would not know how to describe it, but after say 15-20 minutes most components will just sound better. Well, it is not a musical instrument, so it does not sound, but you know what I mean - more pleasing to listen to.
 

Frgirard

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What exactly is happening that makes warm amplifier sound better than the cold one (when it first started)? This in fact applies to the other components as well; phono-stage, pre, ..etc. but is it equally the same?

Can this change be measured?

thanks
My active speakers have the same sound since t=0 until t=10800s but my ears: no.
 

Koeitje

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You just get used to the sound. There is some value in heating up some components, but most reach optimal working temperatures within a minute.
 

xaviescacs

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There is some value in heating up some components, but most reach optimal working temperatures within a minute.

Do you know if that's valid for tubes too? Or they take longer? The manufacturer of my hybrid tube headphone amp specifies that after 20 min the performance reaches its peak but I've never noticed anything. I always assumed that it was true (I have no reason to think otherwise) but totally inaudible.
 

Koeitje

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Do you know if that's valid for tubes too? Or they take longer? The manufacturer of my hybrid tube headphone amp specifies that after 20 min the performance reaches its peak but I've never noticed anything. I always assumed that it was true (I have no reason to think otherwise) but totally inaudible.
Tubes are different I believe, but I have no real knowledge about them.
 

Grumpish

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Depends - a rule of thumb is probably that if it is something that runs hot normally then it will need time to warm up. Tube amps obviously, but SS class A amps as well, on mine the DC offset and bias will both take a good ten minutes to stabilise - confirmed by leaving the meters attached and monitoring the values.
 
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sngreen

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Depends - a rule of thumb is probably that if it is something that runs hot normally then it will need time to warm up. Tube amps obviously, but SS class A amps as well, on mine the DC offset and bias will both take a good ten minutes to stabilise - confirmed by leaving the meters attached and monitoring the values.

By meters you mean the temperature? So this is about DC offset then, warm/hot is where it is meant to be, self-tuning sort of a thing, correct?
 

xaviescacs

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Depends - a rule of thumb is probably that if it is something that runs hot normally then it will need time to warm up. Tube amps obviously, but SS class A amps as well

Then the manufacturer's claim would agree with your statement since my class A hybrid amp runs very hot and takes 20 minutes or so to reach the fusion point, when they say performs better. I haven't measured nor heard anything though.
 

Grumpish

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By meters you mean the temperature? So this is about DC offset then, warm/hot is where it is meant to be, self-tuning sort of a thing, correct?

No, voltage and current - bias is how much current is supplied to the output transistor to keep it in it's operating range, and since in a class A amplifier this also determines the power output it interacts with the DC offset on the output.
 

solderdude

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What exactly is happening that makes warm amplifier sound better than the cold one (when it first started)? This in fact applies to the other components as well; phono-stage, pre, ..etc. but is it equally the same?

Can this change be measured?

thanks

You are not the only one experiencing this. Many folks have noticed this 'effect'

If there is really a change it can be measured.
Some (poorer designed) amplifiers and tube amps require some warm-up time each time when switched on.
Mostly devices that run hot after a while.

One can measure distortion changing (when looking for crossover which is not the same at THD) and frequency response.
Maybe in some tube amps during warm up output R may slightly change.
Some DAC's have chips/Xtals that need to reach an optimum working temp and measurably (not audible) perform slightly 'better.

I the vast majority of cases I would chalk it up to perception. When one listens (while enjoying music) after a while the brain becomes more focussed on music and things in the hearing process 'relax'. The sound is perceived as better. Also the later it gets the better the perception often is.

Now what one can do is leave equipment on and see if the same improvement occurs.
Chances are it doesn't because you know it has been on so are convinced it should already sound optimal.

To check this (over weeks) one would have to really blind test this which is difficult to do so no one will.
 

JSmith

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As soon as I get home every night my amp is turned on and is on all weekend... I never need to worry about this. :D



JSmith
 

charleski

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There are several temperature-dependent processes that can affect an amplifier's operation.

At the most basic level, resistors vary depending on temperature. This is not such a big issue these days, as modern resistors are far more stable over the typical operating range, but old tube amps with dodgy old carbon resistors can see clear fluctuations with temperature.

Transistors very with temperature as well. The most important factor is Vbe, which affects bias. Amp designers need to take care to ensure this is compensated for.

Yes, these changes can all be measured, and should be as part of the design process.
 
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sngreen

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There are several temperature-dependent processes that can affect an amplifier's operation.

At the most basic level, resistors vary depending on temperature. This is not such a big issue these days, as modern resistors are far more stable over the typical operating range, but old tube amps with dodgy old carbon resistors can see clear fluctuations with temperature.

Transistors very with temperature as well. The most important factor is Vbe, which affects bias. Amp designers need to take care to ensure this is compensated for.

Yes, these changes can all be measured, and should be as part of the design process.

That explains it, thank you.
 

GXAlan

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